APEX 2A Facility Receiver APEX Heterodyne Facility APEX 1 Channel Optics APEX 2a Channel Optics Receiver Development Onsala Space Observatory, Sweden, via its Group for Advanced Receiver Development has responsibility for APEX Project heterodyne facility receivers installed in the Nasmyth Cabin A. The facility receivers should cover the following frequencies: Table 1 Band RF range (GHz) IF (GHz) APEX-1 (2SB) 211-275 4-8 APEX-2 (2SB) 275-370 4-8 APEX-3 (2SB) 385-500 4-8 APEX-T2 (BLs) 1320±70 2-4 In order to facilitate availability of the APEX facility heterodyne instruments we proceed our work in two steps, when the First Light Receiver comprises the two receiver channels, APEX 2a with DSB technology (installed at the telescope in March-April 2005) and APEX 1a (2SB) to be placed in the dewar during the fall 2005. First-Light Facility Receiver Figure 1. Inside APEX First Light Receiver: optics, cryogenics and APEX B1 and B2 channel components. The cryostat is a hybrid closed-system using a Gifford Mac-Mahon 2-stage refrigerator, together with a Joule- 400mm Thomson the third stagerefrigerator. The 2-stage gives a temperatures of about 80 K and 15 K for the outer shields. The Joule-Thomson circuitry cools the helium gas further where it condensates with a slight overpressure of 0.2 bar (giving about 4.5 K at sea level and 4.0 K at 5000 m). The cooling takes usually about 12-15 hours. The mixer block is connected directly to the IF 4-8 GHz isolator and to the IF amplifier, to Nasmyth flange minimize losses. A 2nd cold amplifier is on the 15 K 780mm cooling stage. Switching active The receiver optics consists of cold mirrors, one flat mirror and one active, which are combined with another active mirror outside the cryostat. The position and focusing properties of the mirrors and the used corrugated feed horn of the mixer have been chosen such that, with ellipsoid mirror another pair of active mirrors in the Cassegrain cabin, Horn aperture optics produces a frequency independent illumination position for the telescope secondary for the frequency range for each receiver channel in the band of approximately 210-1500 GHz. Figure 2. Optics for the APEX B2A receiver channel, the picture of the First Light Receiver installed at APEX. 6-channel Facility Receiver Development The 6 – channel Facility Receiver with the entire suite The two most challenging receiver channels within of the receiver channels as in the Table above should responsibility of Onsala / GARD for APEX 6-channel be available on the second half of 2006. The two receiver are APEX Band 3 and APEX T2. additional channels, compared to the listed in the We are developing sideband separation technology for Table 1 are APEX 4 (DSB?) 602-700 GHz and APEX 5 the APEX Band 3 385-500 GHz to maximize possible (DSB?) 787-950 GHz. The major challenge in the scientific usefulness of this instrument. designing this 6-chanell receiver is its complexity due to operation at cryogenic temperature 4K, many channels, optical layout and extremely wide frequency range 211- 1500 GHz. In order to achieve the required performance a complex set of mirrors should be used together with perfect cryogenic design and switching mirrors selecting particular channel. Figure 4. APEX 3 mixer chip layout and its matching diagram. Another exciting development is APEX Band T2 1320±70 GHz. In order to be able to cover this extremely high frequencies we will use balanced waveguide mixer with the rectangular waveguide dimensions as small as 90 x 180 μm. 10 μm 1 mm Figure 3. Optical and cryogenic design of 6-channel Figure 5. Scanning Electron Microscope picture of the Facility Receiver. APEX T2 balanced waveguide mixer block.